I know how to set up the default scene by pressing Ctrl+U, but whenever I startup Blender it always fills only one of my screens, even if I set it to fill both before setting the default scene. I end up having to resize it every time I start it up. Is there a way to set this to happen by default?
You can use the menu
Window -> Duplicate Window(Ctrl-Alt-W) - to add a second Blender window, then put one one each monitor. The windows will by "synchronized" as in that changes will be reflected in real time. Ctrl-U will now work to save the setup.
If you want to keep a single window, there is a very dirty trick by using the command line parameters:
If you are using Windows OS, right click on the Blender shortcut icon, add the following code after the path:
-W -p <sx> <sy> <w> <h>
<sx> <sy> represents the lower left corner, e.g. If you have two monitors, both with resolution of 1280*1024, then you would set it like this:
-W -p 0 0 2560 1024
However, you don't want the taskbar overlap on Blender window, a offset is needed:
-W -p 0 30 2560 994
Then, start Blender, the window is in fullscreen mode by default, but the second monitor didn't update at this moment, then you will need to hit AltF11 three times, to keep the window size updated correctly.
The reason I said "it's dirty" is that you have to find your way to update the window. It turns out
-W has to be used. It will be perfect to get rid of it. I'm not sure if this is a bug. And I don't know if this works for other OS. Anyway, it is possible by doing it in this way.
And, no CtrlU needed here.